1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, especially one having a (relatively) shallow junction.
2. Description of the Related Art
Conventionally, to manufacture a semiconductor device which has a narrow junction of about 0.2-0.3 .mu.m in its substrate, the method explained below is generally employed.
First, an insulation film such as an oxidation film is formed on a semiconductor substrate, and a resist pattern is formed on the insulation film. Then, the insulation film is processed into a desired pattern, and ions of an impurity such as As (arsenic) are implanted into the semiconductor substrate, with the resist pattern performing as a mask. After a protection film (or the like) is formed, annealing is carried out and the impurities are electrically activated. Then, the resist pattern is and an aluminum alloy film is formed over all of the substrate. This alloy film is patterned, and an electrode is formed which is electrically connected to the shallow function.
However, in the above-mentioned method, activation of the impurities by annealing is carried out after ions are implanted directly to the semiconductor substrate. Therefore, defects result due to the ions remaining in the substrate during the period of recovery from the damage in the substrate which was caused by the ion implantation. As a result, a regional, abnormal diffusion of the implanted atoms is induced, and junction leak and the like are likely to occur.
Further, when an element having a high vapor pressure such as As is ion-implanted, followed by activation by annealing, As atoms diffuse in the outer direction. Thus, the concentration of the impurity cannot be uniformly maintained successfully uniformed.
Further, when the impurity is ion-implanted in a high concentration, some of the implanted atoms precipitate on the surface of the semiconductor substrate in some cases. The precipitation of these implanted atoms impairs the ohmic contact between the semiconductor substrate and the aluminum alloy when forming the electrode at the shallow junction area.